 /* 给父元素设置伸缩盒 */
 .row{
    display: flex;
}
.row.wrap{
    flex-wrap: wrap;
}
/* 给子元素设置flex设置宽度 */
.col-100{
    flex: 0 0 100%;
}
.col-50{
    flex: 0 0 50%;
}
.col-33{
    flex: 0 0 33.33%;
}
.col-25{
    flex: 0 0 25%;
}
.col-20{
    flex: 0 0 20%;
}
@bili: 15;
@basefont: 750px / @bili;

.bt{
    border-top: 2rem / @basefont solid #f2f2f2;
}
.br{
    border-right: 2rem / @basefont solid #f2f2f2;
}
.bb{
    border-bottom: 2rem / @basefont solid #f2f2f2;
}
.bl{
    border-left: 2rem / @basefont solid #f2f2f2;
}
.floot{
    background-color: #fff;
    margin: 24rem / @basefont;
    overflow: hidden;
    border-radius: 10rem / @basefont;
}
